Surgical needles and attached surgical sutures are widely used medical devices in the medical arts. Surgical sutures are used in most surgical procedures for a variety of functions including tissue repair and approximation, securement of medical devices to tissue including mesh implants, artificial heart valves, etc., and vessel anastomosis and attachment, bone repair, tissue anchoring, etc. In order to have maximum utility to the surgeon during a surgical procedure, it is necessary that the surgical needle have the capability of easily and smoothly penetrating and moving through tissue for multiple passes with minimal force. The amount of force necessary to move a surgical needle through tissue with minimal trauma to the tissue will depend in part on the type of tissue to be penetrated. Various needle designs are available for use with different types of tissue to provide the desired tissue penetration including taper point needles, blunt tip needles, and cutting edge needles. The wire size of the needle will also affect the force to penetrate. In addition, it is known to apply lubricious coatings to surgical needles to improve their penetration and movement through tissue. Lubricious coatings are typically required for implantable or insertable medical devices such as hypodermic needles, surgical needles, and cutting equipment with cutting edges such as knives, scalpels, scissors and blades with cutting edges that contact tissue. The primary purpose of such coatings is to reduce the penetration force and ease the insertion of the device into tissue.
Most conventional lubricious coatings are silicone polymer based. Examples of such silicone materials include the polyalkylsiloxanes. The preferred polyalkylsiloxanes conventionally used are polydimethylsiloxanes. The lubricious silicone coatings may be applied to surgical needles using conventional coating processes known in this art, including dip coating and spraying. Examples of silicone coating compositions and coating processes are contained in the following patent applications which are incorporated by reference: U.S. patent application Ser. Nos. 12/858,489; 12/858,485; 12/858,481; 10/034,636; 10/678,560 (U.S. Pat. No. 7,041,088); Ser. No. 13/162,837 and Ser. No. 12/642,373.
Surgical needles are commonly manufactured using high speed production processes. The production processes typically utilize high speed inline manufacturing lines. Surgical needle blanks are typically mounted to metal carrier strips and moved through the various manufacturing operations, where they are formed in a step-wise process into surgical needles. The manufacturing process steps may include needle point formation, bending, heat treatment, and borehole drilling. In addition, the finished needles may be coated with silicone coatings, e.g., dip coated in silicone coating baths, and moved to drying and curing ovens while on the metal carrier strips. Examples of high speed needle manufacturing processes and equipment are disclosed in the following patents which are incorporated by reference: U.S. Pat. Nos. 5,630,268, 5,644,834, 5,661,893, 5,701,656, 5,776,268, 5,913,875, 6,018,860, and 6,252,195.
Lubricious coatings on most surgical needles are typically applied by conventional dip coating processes, in which the needles are first immersed into a silicone solution, and then drained and exposed to a thermal cycle to remove the solvent and cure the silicone polymer. Other conventional coating processes such as spraying or brushing are also utilized. In a high speed automated production system, surgical needles are coated while mounted to a carrier strip in a semi-continuous manner when employing a dip coating process, wherein a section of the strip is immersed in a tank of the coating solution and then moved out to a blow off device that is used on-line to remove the excess silicone solution prior to a thermal curing step. Although such conventional coating processes are typically effective for their intended purpose, and produce coatings on surgical needles that comply with requirements, there may be some deficiencies associated with conventional dip coating processes using conventional lubricious coatings. Conventional silicone coatings have substantially long cure times and coated needles must be moved to a curing oven while the coating is still wet. The wet coating is susceptible to damage and to being contaminated by dust and dirt particles in the environment, potentially compromising the integrity and performance of the coating. In addition, the wet coatings have a tendency to wick, shrink or move away from the distal end and distal piercing point of the needle, potentially reducing the thickness of the coating to unacceptably low levels and possibly affecting penetration performance.
Accordingly, there is a need in this art for novel coating processes for coating surgical needles with lubricious coatings that provide for improved coating application and coating characteristics.